One known locking sensor for a vehicle safety belt retractor comprises a mass arranged to tip over at a predetermined angle of inclination or level of acceleration. The mass is connected to a rod that engages a base of a lever. When the mass tips over, the rod pushes the lever so that the tip of the lever is moved into engagement with a toothed wheel on the retractor spool. Engagement of the lever tip with the wheel locks the lock cup to the wheel. The lock cup includes a cam surface. As the safety belt pays out further, the spool turns the toothed wheel and thus the lock cup. As the lock cup rotates, the cam surface on the lock cup engages a pivotally mounted locking tooth, pushing the tooth into engagement with a further locking wheel on the spool thus preventing further rotation of the spool. It is the locking tooth engaging the locking wheel that prevents payout of the safety belt.
In the arrangement described, the gap between the lever tip and the ratchet must be closely controlled. If the gap is too large, poor locking performance will result. If the gap is too small, the belt will lock prematurely, erroneously and too frequently. That, in turn, will result in faults due to excessive wear on the retractor components and customer returns.
The gap size is very small and the build up of apparently insignificant manufacturing tolerances can vary the gap and affect the performance of the device quite significantly.
It has been proposed to provide some adjustment means to enable fine tuning of the lever tip position relative to the ratchet. One such example comprises a separate mechanism mounted directly to the retractor frame. The housing and lever are assembled to this mechanism which pivots at one end and is secured at the other by a screw. To adjust the tip gap the screw is loosened, the mechanism rotated about its pivot until the desired gap is obtained and the screw is tightened to hold the mechanism in position to maintain the gap.
That arrangement is rather large and it is difficult to maintain a reliable, consistent gap size from one retractor to another. Each retractor has to be measured and set individually which is time consuming and not readily repeatable.